Abstract

ABSTRACT. For three field seasons (2002/03, 2004/05, 2005/06) we have deployed a network of GPSreceivers and seismometers around the tip of a propagating rift on the Amery Ice Shelf, East Antarctica.During these campaigns we detected seven bursts of episodic rift propagation. To determine whetherthese rift propagation events were triggered by short-term environmental forcings, we analyzedsimultaneous ancillary data such as wind speeds, tidal amplitudes and sea-ice fraction (a proxy variablefor ocean swell). We find that none of these environmental forcings, separately or together, correlatedwith rift propagation. This apparent insensitivity of ice-shelf rift propagation to short-term environmentalforcings leads us to suggest that the rifting process is primarily driven by the internalglaciological stress. Our hypothesis is supported by order-of-magnitude calculations that theglaciological stress is the dominant term in the force balance. However, our calculations also indicatethat as the ice shelf thins or the rift system matures and iceberg detachment becomes imminent, shorttermstresses due to winds and ocean swell may become more important.